US presidential hopeful Kamala Harris and her newly announced running mate Tim Walz continued their reelection campaign in the battleground states of Michigan and Wisconsin on Wednesday.

Harris told the day’s first rally in Eau Claire, Wisconsin, that, "As Tim Walz likes to point out, we are joyful warriors."

Contributing to that feeling, the Harris campaign said it had raised $36 million in the first 24 hours after she announced Walz as her running mate.

Crowds chant 'VP Walz!' at Wisconsin rally

The vice president introduced Walz to a raucous crowd and played up his Midwestern roots, while often referring to him as "coach," a nod to his past as a high school football coach.

Harris referred to Walz as "the next vice president" with people then chanting: “VP Walz!” Her campaign said more than 12,000 people attended the rally.

She said the pair look to the future with optimism unlike Republican presidential nominee Donald Trump and his vice presidential nominee JD Vance.

Vance was also in the same Wisconsin city at the same time as he looks to introduce himself to voters on behalf of the Republican ticket.

Harris attacked Trump at the rally, saying, "Someone who suggests we should terminate the Constitution of the United States should never again have the chance to sit behind the seal of the United States."

Harris, Walz build momentum in 'Blue Wall' states

Harris and Walz will then tour Detroit, Michigan. The rallies come a day after the duo kicked off their joint campaign in Pennsylvania.

The two states — Wisconsin and Michigan — are part of the "Blue Wall" that Democrats will need to win to elect Harris to the White House.

Wisconsin and Michigan will also be an early test for the Midwestern credentials of Walz, who served as the governor of nearby Minnesota.

Trump calls Walz a 'shocking pick'

Earlier on Wednesday, former president and current Republican nominee Trump slammed Harris and Walz in an interview on the breakfast TV show "Fox & Friends."

Trump called Walz a "shocking pick" and sought to paint him as a radical progressive sidekick for Harris.

"He's a smarter version of her," Trump said.

Trump also said he was keen to debate Harris after he said he would skip a scheduled debate on broadcaster ABC with the Democratic nominee after US President Joe Biden pulled out of the race.

Trump has instead, in a social media post, called on his own for a debate with Harris on the conservative-friendly Fox network with a live audience.  

"I hear she's sort of a nasty person but not a good, good debater. But we'll see because we'll be debating her, I guess in the pretty near future. It's going to be announced fairly soon but we'll be debating her," Trump said.

Trump previously said he would prefer to debate Harris on Fox, which is perceived as being friendlier to him, but also said that "every network loves me very much right now."

rm, zc/wd (Reuters, AP)